Some people might not be interested in murder, but I have not met them. Indeed, whenever conversation flags at a dinner party, I usually try to revive it with tales of the murderers I have known as a prison doctor. The method usually worksthough only after my fellow-guests have expressed a socially obligatory frisson of horror before immersing themselves mentally in gore, usually with enthusiasm.

Why should murder be so perennially and universally interesting? Literature, to say nothing of popular films, would find itself much denuded without it. Whole bookshops would go out of business if people suddenly lost interest in murder, and our newspapers would be dull indeed without it.

The answer supplied in The Murderer Next Door: Why the Mind Is Designed to Kill, by David M. Buss, Professor of Psychology at the University of Texas at Austin, is that murder is part of the inbuilt repertoire of human behavior that evolution has shaped. This fact does not mean that we are all murderers; merely that we are all potentially murderers, and our interest in murder is therefore the tribute that potentiality, or even desire, pays to accomplishment.

Busss clearly-written account, mercifully jargon-free, is based upon his wide reading, his study of the detailed individual records of murders committed in Michigan, analyses of FBI statistics concerning half a million murders, and surveys of large numbers of people in different countries about their murderous fantasies. The idea of killing someone has apparently occurred, at least fleetingly, to most people. Buss has examined the circumstances in which such fantasies occurred, on the not unnatural supposition that real murder is the consequence, albeit infrequent, of murderous ideas.

Busss work forms part of a great contemporary wave of sociobiological thought about evolution that, after the demise of Freudianism and Marxism, is the current contender for the grand unifying theory that explains the whole of man to himself. In this field one finds a tremendous amount of fascinating and often recondite information, combined with ingenious theorizing (or special pleading), which produces truisms or platitudes that one could have arrived at with the expenditure of much less effort.

The theory of murder propounded in this book is roughly as follows. The primary and overarching goal of humans is to spread their seed, or genes, as widely as possible. Their psychology has evolved to enable them to do so; but because women can have only a few children in their lifetimes, while men face no such limit, the psychologies of men and women, and therefore their reasons for committing murder, are different.

Men are by nature polygamous, women monogamous. Men want a harem, women a husband. Men are by nature protective of their exclusive sexual possession of women, or of the reputation that establishes them in the eyes of other men as formidable protectors of their women-folk, in other words of their honor; women, by contrast, are protective of the attributes, including the reputation for fidelity, that make them desirable mothers of children.

While a man, sociobiologically speaking, seeks a beautiful young woman as the (or a) mother of his childrenbeauty being a biological metonym for healtha woman seeks a man who is of high social status, because he will be a better, more secure provider for their children. This distinction helps to explain why men are much more likely to kill in response to public humiliation than women, and also why murder is, statistically speaking, a lower-class crime. Lower class men are more sensitive to insult because they have nothing to offer women except raw physical power, an asset that declines sharply with age. If they fail to display such raw physical power in response to a public challenge or humiliation, their value as a potential mate vanishes altogether. They face genetic oblivion.

Women tend to kill in response to threats from jealous, controlling, violent men. Men kill women who are, or whom they believe to be, unfaithful, because an unfaithful woman might give birth to a child by another man, whom the cuckolded man will then devote his energies to raising, to the detriment of his own biological offspring, either potential or actual. Men are also likely to kill those men whom they see as direct competitors in the mating game, or those who reduce their chances of success in that game because of superior accomplishments. The fact that murder nowadays, thanks to the operation of the law, is hardly the royal road to reproductive success, is explained away by Buss by the absence of police forces, law courts, and so forth at the time when the propensity to murder first evolved. Such a propensity would have served men well on the savannahs of East Africa, where man first emerged.

All this fits quite well with the data, as does the fact that stepfathers are 40 times more likely to kill a stepchild than is a biological father to kill his child. A stepfather wants his woman to attend to his offspring, not those of another man (do not lions routinely kill the cubs of the lionesss former impregnator?). But the example of stepchildren actually demonstrates the limitations of sociobiological explanation as well as its strengths: for the fact is that, even if stepfathers kill stepchildren 40 times more often than biological parents, only one in 2,000 stepchildren dies at his stepfathers hand.

With this statistic in mind, it follows that the best reproductive strategy for men, if they were really concerned mainly to spread their genes, would be to father as many children as possible, and then desert them to the care of stepfathers, secure in the knowledge that only one in 2,000 of their children will be killed. The time that a biological father would otherwise have devoted towasted insupporting his own offspring would now be free to devote to impregnating hundreds or thousands of women and thereby spreading his genes far and wide. Meanwhile, hundreds or thousands of foolish stepfathers would be raising children who were not theirs, and in the process putting themselves hors de combat in the biological competition.

One might argue that something approaching this state of affairs has developed in the western worlds lower-class ghettoes. But then why has it not existed throughout human history, if the principle determinant of human behavior were of the kind sociobiologists propose?

There is nothing in Busss book as to why the murder rate in the United States was 1.5 per 100,000 in 1900 and 10 per 100,000 in 1990 (and the rate would have been 50 per 100,000 if not for improvements in the medical treatment of trauma). There is nothing either as to why the murder rate in Japan was one eleventh that of the United States in 1990. Are the Japanese sociobiologically different from the Americans? Were the Americans of a century ago sociobiologically different from the Americans of today?

The explanatory force of sociobiology, contrary to its practitioners claims, is slight when it comes to human behaviorprecisely where the disciplines aspirations are greatest. At best, sociobiology sets the outer limits of human possibility: for example, it suggests that a world of painless free love, such as the utopian adolescents of the 1960s proposed to bring about, is not possible. But then no sensible or cultivated person ever supposed for a moment that it would be possible. Sociobiology no doubt brings crumbs to the feast of human self-understanding, but nothing more.